section_40078021adasad27814

Sub-Bases,Bases (Non-Bituminous)and Shoulders

400

Sub-Bases,Bases(Non-Bituminous) andShoulders

112

Section 400 Sub-Bases,Bases (Non-Bituminous) and Shoulders

113

Sub-Bases,Bases (Non-Bituminous) and Shoulders Section 400

401 GRANULAR SUB-BASE

401.1 Scope

This work shall consist of laying and compacting well-graded material on prepared subgradein accordance with the requirements of these Specifications. The material shall be laid inone or more layers as sub-base or lower sub-base and upper sub-base (termed as sub-base hereinafter) as necessary according to lines, grades and cross-sections shown onthe drawings or as directed by the Engineer.

401.2 Materials

401.2.1 The material to be used for the work shall be natural sand, crushed gravel,crushed stone, or combination thereof depending upon the grading required. The materialshall be free from organic or other deleterious constituents and shall conform to the qualitystandards as prescribed in the specifications.

Table 400-1 prescribes four gradings for Granular Sub-Base (GSB). Gradings I and II inTable 400-1 are well graded granular sub-base materials. These can be used at locationswhere drainage requirement are not predominant. Gradings III and IV are gap graded andaddresses to the concern of the drainage requirements. These can be used at locationexperiencing heavy rainfall, flooding etc. Cases where GSB is to be provided in two layers,it is recommended to adopt either grading III or grading IV for lower layer and either gradingI or grading II for upper layer. Minimum thickness of lower layer at locations where drainagerequirements are predominant shall not be less than 200 mm. The grading to be adoptedfor a project shall be as specified in the Contract.

401.2.2 Physical requirements: The material shall have a 10 percent fines value of50kN or more (for sample in soaked condition) when tested in compliance with IS:2386(Part IV) 1963. The water absorption value of the coarse aggregate shall be determinedas per IS:2386 (Part 3). If this value is greater than 2 percent, the soundness test shall becarried out on the material delivered to site as per IS:383. For Gradings II and IV materials,the CBR shall be determined at the density and moisture content likely to be developed inthe field.

401.3 Strength of Sub-Base

It shall be ensured prior to actual execution that the material to be used in the sub-basesatisfies the requirements of CBR and other physical requirements when compacted andfinished.

When directed by the Engineer, this shall be verified by performing CBR tests in thelaboratory as required on specimens remoulded at field dry density and moisture content.

114


Table 400-1 Grading for Granular Sub-base Materials

IS Sieve Percent by weight passing the IS sieve

Designation Grading I Grading II Grading III Grading IV

75.0 mm 100 — 100 —53.0 mm 80-100 100 10026.5 mm 55 –90 70-100 55-75 50-809.50 mm 35-65 50-804.75 mm 25 – 55 40-65 10-30 15-352.36 mm 20- 40 30-500.425 mm 10-15 10- 150.075 mm <5 < 5 < 5 < 5

CBR Value (Minimum) 30 25 30 25

Note: The material passing 425 micron (0.425 mm) sieve for all the gradings whentested according to IS:2720 (Part 5) shall have liquid limit and plasticity indexnot more than 25 and 6 percent respectively.

401.4 Construction Operations

401.4.1 Preparation of subgrade : Immediately prior to the laying of sub-base, thesubgrade already finished to Clause 301 or 305 as applicable shall be prepared byremoving all vegetation and other extraneous matter, lightly sprinkled with water, if necessaryand rolled with two passes of 80–100 kN smooth wheeled roller.

401.4.2 Spreading and compacting : The sub-base material of grading specifiedin the Contract shall be spread on the prepared subgrade with the help of a motor graderof adequate capacity, its blade having hydraulic controls suitable for initial adjustment andfor maintaining the required slope and grade during the operation or other means asapproved by the Engineer.

When the sub-base material consists of combination of materials mentioned in Clause401.2.1, mixing shall be done mechanically. Mixing shall be done in a separate yard bypugmill or other approved mechanical means so as to issue homogenous & uniform mix.

Moisture content of the loose material shall be checked in accordance with IS:2720 (Part2) and suitably adjusted by sprinkling additional water from a truck mounted or trailermounted water tank and suitable for applying water uniformly and at controlled quantitiesto variable widths of surface or other means approved by the Engineer so that, at the timeof compaction, it is from 1 percent above to 2 percent below the optimum moisture contentcorresponding to IS:2720 (Part 8). While adding water, due allowance shall be made forevaporation losses. After water has been added, the material shall be processed bymechanical or other approved means until the layer is uniformly wet.

115


Immediately thereafter, rolling shall start. If the thickness of the compacted layer does notexceed 100 mm, a smooth wheeled roller of 80 to 100 kN weight may be used. For acompacted single layer upto 200 mm the compaction shall be done with the help of avibratory roller of minimum 80 to 100 kN static weight with plain drum or pad foot-drum orheavy pneumatic tyred roller of minimum 200 to 300 kN weight having a minimum tyrepressure of 0.7 MPa or equivalent capacity roller capable of achieving the requiredcompaction. Rolling shall commence at the lower edge and proceed towards the upperedge longitudinally for portions having unidirectional crossfall and super-elevation shallcommence at the edges and progress towards the centre for portions having crossfall onboth sides.

Each pass of the roller shall uniformly overlap not less than one-third of the track made inthe preceding pass. During rolling, the grade and crossfall (camber) shall be checked andany high spots or depressions which become apparent, corrected by removing or addingfresh material. The speed of the roller shall not exceed 5 km per hour.

Rolling shall be continued till the density achieved is at least 98 percent of the maximumdry density for the material determined as per IS:2720 (Part 8). The surface of any layer ofmaterial on completion of compaction shall be well closed, free from movement undercompaction equipment and from compaction planes, ridges, cracks or loose material. Allloose, segregated or otherwise defective areas shall be made good to the full thickness oflayer and re-compacted.

401.5 Surface Finish and Quality Control of Work

The surface finish of construction shall conform to the requirements of Clause 902. Controlon the quality of materials and works shall be exercised by the Engineer in accordancewith Section 900.

401.6 Arrangements for Traffic

During the period of construction, arrangements for the traffic shall be provided andmaintained in accordance with Clause 112.

401.7 Measurements for Payment

Granular sub-base shall be measured as finished work in position in cubic metres.

The protection of edges of granular sub-base extended over the full formation as shown inthe drawing shall be considered incidental to the work of providing granular sub-base andas such no extra payment shall be made for the same.

116


401.8 Rate

The Contract unit rate for granular sub-base shall be payment in full for carrying out therequired operations including full compensation for:

i) making arrangements for traffic to Clause 112 except for initialtreatment to verges, shoulders and construction of diversions;

ii) furnishing all materials to be incorporated in the work including allroyalties, fees, rents where applicable with all leads and lifts;

iii) all labour, tools, equipment and incidentals to complete the work tothe Specifications;

iv) carrying out the work in part widths of road where directed; and

v) carrying out the required tests for quality control.

402 LIME TREATED SOIL FOR IMPROVED SUB-GRADE/SUB-BASE

402.1 Scope

This work shall consist of laying and compacting an improved sub-grade/lower sub-baseof soil treated with lime on prepared sub-grade in accordance with the requirements ofthese Specifications and in conformity with the lines, grades and cross-sections shown onthe drawings or as directed by the Engineer. Lime treatment is generally effective for soilswhich contain a relatively high percentage of clay and silty clay.

402.2 Materials

402.2.1 Soil : Except when otherwise specified, the soil used for stabilization shallbe the local clayey soil having a plasticity index greater than 8.

402.2.2 Lime : Lime for lime-soil stabilization work shall be commercial dry limeslaked at site or pre-slaked lime delivered to the site in suitable packing. Unless otherwisepermitted by the Engineer, the lime shall have purity of not less than 70 percent by weightof Quick-lime (CaO) when tested in accordance with IS:1514. Lime shall be properlystored to avoid prolonged exposure to the atmosphere and consequent carbonation whichwould reduce its binding properties.

402.2.3 Quantity of lime in stabilized mix : Quantity of lime to be added aspercentage by weight of the dry soil shall be as specified in the Contract. The quantity oflime used shall be related to its calcium oxide content which shall be specified. Where thelime of different calcium oxide content is to be used, its quantity shall be suitably adjustedto the approval of the Engineer so that equivalent calcium oxide is incorporated in thework. The mix design shall be done to arrive at the appropriate quantity of lime to be

117


added, having due regard to the purity of lime, the type of soil, the moisture-densityrelationship, and the design CBR/Unconfined Compressive Strength (UCS) value specifiedin the Contract. The laboratory CBR/UCS value shall be at least 1.5 times the minimumfield value of CBR/UCS stipulated in the Contract.

402.2.4 Water : The water to be used for lime stabilisation shall be clean and freefrom injurious substances. Potable water shall be preferred.


402.3.1 Weather limitations : Lime-soil stabilisation shall not be done when the airtemperature in the shade is less than 100 C.

402.3.2 Degree of pulverisation : For lime stabilisation, the soil before addition ofstabilizer, shall be pulverized using agricultural implements like disc harrows (only for lowvolume roads) and rotavators to the extent that it passes the requirements set out in Table400-2 when tested in accordance with the method described in Appendix 3.

Table 400-2 Soil Pulverisation Requirements for Lime Stabilisation

IS Sieve Minimum percent by weightdesignation passing the IS Sieve

26.5 mm 1005.6 mm 80

402.3.3 Equipment for construction : Stabilised soil sub-bases shall beconstructed by mix-in-place method of construction or as otherwise approved by theEngineer. Manual mixing shall be permitted only where the width of laying is not adequatefor mechanical operations, as in small-sized jobs.

The equipment used for mix-in-place construction shall be a rotavator or similar approvedequipment capable of pulverizing and mixing the soil with additive and water to specifieddegree to the full thickness of the layer being processed, and of achieving the desireddegree of mixing and uniformity of the stabilized material. If so desired by the Engineer,trial runs with the equipment shall be carried out to establish its suitability for work.

The thickness of any layer to be stabilized shall be not less than 100 mm when compacted.The maximum thickness can be 200 mm, provided the plant used is accepted by theEngineer.

402.3.4 Mix-in-place method of construction : Before deploying the equipment,the soil after it is made free of undesirable vegetation or other deleterious matter shall be

118


spread uniformly on the prepared subgrade in a quantity sufficient to achieve the desiredcompacted thickness of the stabilised layer. Where single-pass equipment is to beemployed, the soil shall be lightly rolled at the discretion of the Engineer.

The equipment used shall either be of single-pass or multiple pass type. The mixers shallbe equipped with an appropriate device for controlling the depth of processing and themixing blades shall be maintained or reset periodically so that the correct depth of mixingis obtained at all times.

With single-pass equipment the forward speed of the machine shall be so selected inrelation to the rotor speed that the required degree of mixing, pulverisation and depth ofprocessing is obtained. In multiple-pass processing, the prepared sub-grade shall bepulverised to the required depth with successive passes of the equipment and the moisturecontent adjusted to be within prescribed limits mentioned hereinafter. The blending orstabilizing material shall then be spread uniformly and mixing continued with successivepasses until the required depth and uniformity of processing have been obtained.

The mixing equipment shall be so set that it cuts slightly into the edge of the adjoining laneprocessed previously so as to ensure that all the material forming a layer has been properlyprocessed for the full width.

402.3.5 Construction with manual means : Where manual mixing is permitted,the soil from borrow areas shall first be freed of all vegetation and other deleterious materand placed on the prepared subgrade. The soil shall then be pulverized by means ofcrow-bars, pick axes or other means approved by the Engineer.

Water in requisite quantities may be sprinkled on the soil for aiding pulverisation. On thepulverized soil, the blending material(s) in requisite quantities shall be spread uniformlyand mixed thoroughly by working with spades or other similar implements till the wholemass is uniform. After adjusting the moisture content to be within the limits mentionedlater, the mixed material shall be leveled up to the required thickness so that it is ready tobe rolled.

402.3.6 Addition of lime : Lime may be mixed with the prepared material either inslurry form or dry state at the option of the Contractor with the approval of the Engineer.

Dry lime shall be prevented from blowing by adding water to the lime or other suitablemeans selected by the Contractor, with the approval of the Engineer.

The tops of windrowed material may be flattened or slightly trenched to receive the lime.The distance to which lime may be spread upon the prepared material ahead of the mixingoperation shall be determined by the Engineer.

No traffic other than the mixing equipment shall be allowed to pass over the spread limeuntil after completion of mixing.

119


Mixing or remixing operations, regardless of equipment used, shall continue until the materialis free of any white streaks or pockets of lime and the mixture is uniform.

Non-uniformity of colour reaction, when the treated material is tested with the standardphenolphthalein alcohol indicator, will be considered evidence of inadequate mixing.

402.3.7 Moisture content for compaction : The moisture content at compactionchecked vide IS:2720 (Part 2) shall neither be less than the optimum moisture contentcorresponding to IS:2720 (Part 8) nor more than 2 percent above it.

402.3.8 Rolling : Immediately after spreading, grading and levelling of the mixedmaterial, compaction shall be carried out with approved equipment preceded by a fewpasses of lighter rollers if necessary. Rolling shall commence at edges and progresstowards the centre, except at super elevated portions where it shall commence at the inneredge and progress towards the outer edge. During rolling, the surface shall be frequentlychecked for grade and crossfall (camber) and any irregularities corrected by looseningthe material and removing/adding fresh material. Compaction shall continue until the densityachieved is at least 98 percent of the maximum dry density for the material determined inaccordance with IS:2720 (Part 8).

Care shall be taken to see that the compaction of lime stabilised material is completedwithin three hours of its mixing or such shorter period as may be found necessary in dryweather.

During rolling it shall be ensured that roller does not bear directly on hardened or partiallyhardened treated material previously laid other than what may be necessary for achievingthe specified compaction at the joint. The final surface shall be well closed, free frommovement under compaction planes, ridges, cracks or loose material. All loose orsegregated or otherwise defective areas shall be made good to the full thickness of thelayer and recompacted.

402.3.9 Curing : The sub-base course shall be suitably cured for a minimum periodof 7 days after which subsequent pavement courses shall be laid to prevent the surfacefrom drying out and becoming friable. No traffic of any kind shall ply over the completedsub-base unless permitted by the Engineer.


The surface finish of construction shall conform to the requirements of Clause 902.

Control on the quality of materials and works shall be exercised by the Engineer inaccordance with Section 900.

120


402.5 Strength

When lime is used for improving the subgrade, the soil-lime mix shall be tested for its CBRvalue. When lime stabilized soil is used in a sub-base, it shall be tested for unconfinedcompressive strength (UCS) at 7 days. In case of variation from the design CBR/UCS, insitu value being lower, the pavement design shall be reviewed based on the actual CBR/UCS values. The extra pavement thickness needed on account of lower CBR/UCS valueshall be constructed by the Contractor at his own cost.


During the period of construction, arrangements for traffic shall be provided and maintainedin accordance with Clause 112.


Stabilised soil sub-base shall be measured as finished work in position in cubic metres.

402.8 Rate

The Contract unit rate for lime stabilised soil sub-base shall be payment in full for carryingout the required operations including full compensation for all components listed in Clause401.8 (i) to (v).

403 CEMENT TREATED SOIL SUB-BASE/BASE

403.1 Scope

This work shall consist of laying and compacting a sub-base/base course of soil treatedwith cement on prepared subgrade/sub-base, in accordance with the requirements of theseSpecifications and in conformity with the lines, grades and cross-sections shown on thedrawings or as directed by the Engineer.

403.2 Materials

403.2.1 Material to be stabilised : The material used for cement treatment shall besoil including sand and gravel, laterite, kankar, brick aggregate, crushed rock or slag orany combination of these. For use in a sub-base course, the material shall have a gradingshown in Table 400-3(a). It shall have a uniformity coefficient not less than 5, capable ofproducing a well-closed surface finish. For use in a base course, the material shall besufficiently well graded to ensure a well-closed surface finish and have a grading within therange given in Table 400-3. If the material passing 425 micron sieve is plastic, it shallhave a liquid limit not greater than 45 percent and a plasticity index not greater than20 percent determined in accordance with IS:2720 (Part 5). The physical requirements

121


for the material to be treated with cement for use in a base course shall be same as forGrading I Granular Sub-base, Clause 401.2.2.

403.2.2 Cement : Cement for stabilization shall either be ordinary portland cement,portland slag cement or portland puzzolana cement and shall comply with the requirementsof IS:269, 455 or 1489 respectively.

Table 400-3 Grading Limits of Material for Stabilisation with Cement

IS sieve size Percentage by mass passing

Sub-Base/BaseWithin the range

53.00 mm 10037.5 mm 95 – 10019.0 mm 45 – 1009.5 mm 35 – 1004.75 mm 25 – 100600 micron 8 – 65300 micron 5 – 4075 micron 0 – 10

403.2.3 Lime : If needed for pre-treatment of highly clayey soils, Clause 402.2.2shall apply.

403.2.4 Quantity of cement in stabilised mix : The quantity of cement to be addedas percent by weight of the dry soil shall be specified in the Contract. Also if lime is usedas pretreatment for highly clayey soils, the quantity as percent by weight of dry soil shall bespecified in the Contract. The mix design shall be done on the basis of 7 day unconfinedcompressive strength (UCS) and/or durability test under 12 cycles of wet-dry conditions.The laboratory strength values shall be at least 1.5 times the minimum field UCS valuestipulated in the Contract.

403.2.5 Water : The water to be used for cement stabilization shall be clean and freefrom injurious substances. Potable water shall be preferred.


403.3.1 Weather limitations : Stabilisation shall not be done when the airtemperature in the shade is less than 10°C.

403.3.2 Degree of pulverisation : For stabilisation, the soil before addition ofstabilizer, shall be pulverised, where necessary, to the extent that it passes the requirements

122


as set out in Table 400-4 when tested in accordance with the method described inAppendix 3.

Table 400-4 Soil Pulverisation Requirements for Cement Stabilisation

IS sieve Designation Minimum per cent by weight passing the IS sieve

26.5 mm 1005.6 mm 80

403.3.3 Clauses 402.3.3 to 402.3.5 shall apply as regards spreading and mixingthe stabilizer except that cement or lime plus cement as the case may be, shall be used asthe stabilizing material.

403.3.4 Moisture content for compaction : The moisture content at compactionchecked vide IS:2720 (Part 2) shall not be less than the optimum moisture contentcorresponding to IS:2720 (Part 8) nor more than 2 per cent above it.

403.3.5 Rolling : Clause 402.3.8 shall apply except that care shall be taken to seethat the compaction of cement stabilised material is completed within two hours of itsmixing or such shorter period as may be found necessary in dry weather.

403.3.6 Curing : The sub-base/base course shall be suitably cured for 7 days.Subsequent pavement course shall be laid soon after to prevent the surface from dryingout and becoming friable. No traffic of any kind shall ply over the completed sub-baseunless permitted by the Engineer.

403.4 Surface Finish and Quality Control of Works


403.5 Strength

Control on the quality of materials and works shall be exercised by the Engineer inaccordance with Section 900.

Cement treated soil sub-base/base shall be tested for the unconfined compressive strength(UCS) value at 7 days, actually obtained in-situ. In case of variation from the design UCS,in-situ value being on lower side, prior to proceeding with laying of base/surface course onit, the pavement design shall be reviewed for actual UCS value. The extra pavementthickness needed on account of lower UCS shall be constructed by the Contractor at hisown cost.

123



During the period of construction, arrangements for traffic shall be provided and maintainedin accordance with Clause 112.


Stabilised soil sub-base/base shall be measured as finished work in position in cubicmetres.

403.8 Rate

The Contract unit rate for cement treated soil sub-base/base with pretreatment with lime ifrequired shall be payment in full for carrying out required operations including fullcompensation for all components listed in Clause 401.8 (i ) to (v).

404 WATER BOUND MACADAM SUB-BASE/BASE

404.1 Scope

This work shall consist of clean crushed aggregates mechanically interlocked by rollingand bonding together with screening, binding material where necessary and water laid ona properly prepared subgrade/sub-base/base or existing pavement, as the case may beand finished in accordance with the requirements of these Specifications and in closeconformity with the lines, grades, cross-sections and thickness as per approved plans oras directed by the Engineer. This specification is meant for repairs and minor works ofwidening nature, and also at locations where it is not feasible to lay WMM.

404.2 Materials

404.2.1 Coarse aggregates : Coarse aggregates shall be either crushed or brokenstone, crushed slag, overburnt (Jhama) brick aggregates or any other naturally occurringaggregates such as kankar and laterite of suitable quality. Materials other than crushed orbroken stone and crushed slag shall be used in sub-base courses only. If crushed gravel/shingle is used, not less than 90 percent by weight of the gravel/shingle pieces retainedon 4.75 mm sieve shall have at least two fractured faces. The aggregates shall conform tothe physical requirements set forth in Table 400-5. The type and size range of the aggregateshall be specified in the Contract or shall be as specified by the Engineer. If the waterabsorption value of the coarse aggregate is greater than 2 percent, the soundness testshall be carried out on the material delivered to site as per IS:2386 (Part 5).

124


Table 400-5 Physical Requirements of Coarse Aggregates for Water BoundMacadam for Sub-base/Base Courses

S.No. Test Test Method Requirements

1. Los Angeles IS: 2386 40 percent (Max)Abrasion value (Part 4)

Aggregate IS: 2386 30 percent (Max)Impact value (Part-4) or

IS:5640*

2. Combined IS:2386 40 percent (Max)Flakiness and (Part-1)ElongationIndices (Total) **

* Aggregates which get softened in presence of water shall be tested for Impactvalue under wet conditions in accordance with IS:5640.

** The requirement of flakiness index and elongation index shall be enforced only inthe case of crushed broken stone and crushed slag.

404.2.2 Crushed or broken stone : The crushed or broken stone shall be hard,durable and free from excess flat, elongated, soft and disintegrated particles, dirt andother deleterious material.

404.2.3 Crushed slag : Crushed slag shall be made from air-cooled blast furnaceslag. It shall be of angular shape, reasonably uniform in quality and density and generallyfree from thin, elongated and soft pieces, dirt or other deleterious materials. The weight ofcrushed slag shall not be less than 11.2 kN per m3 and the percentage of glossy materialshall not be more than 20. It should also comply with the following requirements:

i) Chemical stability : To comply with requirements ofappendix of BS:1047.

ii) Sulphur content : Maximum 2 percentiii) Water absorption : Maximum 10 percent

404.2.4 Overburnt (Jhama) brick aggregates : Jhama brick aggregates shall bemade from overburnt bricks or brick bats and be free from dust and other objectionableand deleterious materials. This shall be amount only for road stretch when traffic is low.

404.2.5. Grading requirement of coarse aggregates : The coarse aggregatesshall conform to one of the Gradings given in Table 400-6 as specified, provided, however,the use of Grading No.1 shall be restricted to sub-base courses only.

125


Table 400-6 Grading Requirements of Coarse Aggregates

Grading Size Range IS Sieve Per cent byNo. Designation weight passing

1. 63 mm to 45 mm 75 mm 10063 mm 90 – 10053 mm 25 – 7545 mm 0 – 1522.4 mm 0 – 5

2. 53 mm to 22.4 mm 63 mm 10053 mm 95 – 10045 mm 65 – 9022.4 mm 0 – 1011.2 mm 0 – 5

Note: The compacted thickness for a layer shall be 75 mm.

404.2.6 Screenings : Screenings to fill voids in the coarse aggregate shall generallyconsist of the same material as the coarse aggregate. However, where permitted,predominantly non-plastic material such as moorum or gravel (other than rounded riverborne material) may be used for this purpose provided liquid limit and plasticity index ofsuch material are below 20 and 6 respectively and fraction passing 75 micron sieve doesnot exceed 10 percent.

Screenings shall conform to the grading set forth in Table 400-7. The consolidated detailsof quantity of screenings required for various grades of stone aggregates are given inTable 400-8. The table also gives the quantities of materials (loose) required for 10 m2 forsub-base/base compacted thickness of 75 mm.

The use of screenings shall be omitted in the case of soft aggregates such as brick metal,kankar, laterites, etc. as they are likely to get crushed to a certain extent under rollers.

404.2.7 Binding material : Binding material to be used for water bound macadamas a filler material meant for preventing ravelling shall comprise of a suitable materialapproved by the Engineer having a Plasticity Index (PI) value of less than 6 as determinedin accordance with IS:2720 (Part-5).

The quantity of binding material where it is to be used, will depend on the type of screenings.Generally, the quantity required for 75 mm compacted thickness of water bound macadamwill be 0.06–0.09 m3 per 10 m2.

126


Table 400-7 Grading For Screenings

Grading Size of Screenings IS Sieve Designation Per cent by weightClassification passing the sieve

A 13.2 mm 13.2 mm 10011.2 mm 95 – 1005.6 mm 15 - 35180 micron 0 –10

B 1.2 mm 11.2 mm 1005.6 mm 90 – 100180 micron 15 – 35

Table 400-8 Approximate Quantities of Coarse Aggregates and ScreeningsRequired for 75 mm Compacted Thickness of Water Bound

Macadam (WBM) Sub-base/Base Course for 10m2 Area

Classifi- Size Compacted Loose Screeningscation Range thickness Qty. Stone Screening Crushable type such

as Moorum or Gravel

Grading For Grading LooseClassifi- WBM Classi- Qty.cation & Sub-base/ ficationSize base & Size

course(Loosequantity)

Grading 1 63 mm to 75 mm 0.91 to Type A 0.12 to Not 0.22 to45 mm 1.07 m3 13.2 mm 0.15 m3 uniform 0.24 m3

-do- -do- -do- -do- Type B 0.20 to -do- -do-11.2 mm 0.22 m3

Grading 2 53 mm to 75 mm -do- -do- 0.18 to -do- -do-22.4 mm 0.21 m3

The above mentioned quantities should be taken as a guide only, for estimation of quantities

for construction etc.

Application of binding materials may not be necessary when the screenings used are of

crushable type such as moorum or gravel.

127



404.3.1 Preparation of base : The surface of the sub-grade/sub-base/base toreceive the water bound macadam course shall be prepared to the specified grade andcamber and cleaned of dust, dirt and other extraneous material. Any ruts or soft yieldingplaces shall be corrected in an approved manner and rolled until firm surface is obtained.

Where the WBM is to be laid on an existing metalled road, damaged area includingdepressions and potholes shall be repaired and made good with the suitable material.The existing surface shall be scarified and re-shaped to the required grade and camberbefore spreading the coarse aggregate for WBM.

As far as possible, laying water bound macadam course over existing bituminous layermay be avoided since it will cause problems of internal drainage of the pavement at theinterface of two courses. It is desirable to completely pick out the existing thin bituminouswearing course where water bound macadam is proposed to be laid over it.

404.3.2 Inverted choke/sub surface drainage layer : If water bound macadam isto be laid directly over the sub-grade, without any other intervening pavement course, a 25mm course of screenings (Grading B) or coarse sand shall be spread on the preparedsub-grade before application of the aggregates is taken up. In case of a fine sand or siltyor clayey sub-grade, it is advisable to lay 100 mm insulating layer of screening or coarsesand on top of fine grained soil, the gradation of which will depend upon whether it isintended to act as a drainage layer as well. As a preferred alternative to inverted choke,appropriate geosynthetics performing functions of separation and drainage may be usedover the prepared sub-grade as directed by the Engineer. Section 700 shall be applicablefor use of geosynthetics.

404.3.3 Lateral confinement of Aggregates : For construction of WBM,arrangement shall be made for the lateral confinement of aggregates. This shall be doneby building adjoining shoulders along with WBM layers. The practice of constructing WBMin a trench section excavated in the finished formation must be completely avoided.

Where the WBM course is to be constructed in narrow widths for widening of an existingpavement, the existing shoulders should be excavated to their full depth and width up tothe sub-grade level except where widening specifications envisages laying of a stablisedsub-base using in-situ operations in which case the same should be removed only up tothe sub-base level.

404.3.4 Spreading coarse aggregates : The coarse aggregates shall be spreaduniformly and evenly upon the prepared sub-grade/sub-base in the required quantitiesfrom the stockpiles to proper profile by using templates placed across the road about 6 mapart, in such quantities that the thickness of each compacted layer is not more than 75mm. In no case shall these be dumped in heaps directly on the area where these are to be

128


laid nor shall their hauling over a partly completed base be permitted. Wherever possible,approved mechanical devies such as aggregate spreader shall be used to spread theaggregates uniformly so as to minimize the need for manual rectification afterwards.

No segregation of coarse or fine aggregates shall be allowed and the coarse aggregates,as spread shall be of uniform gradation with no pockets of fine material.

The surface of the aggregates spread shall be carefully checked with templates and allhigh or low spots remedied by removing or adding aggregates as may be required. Thesurface shall be checked frequently with a straight edge while spreading and rolling so asto ensure a finished surface as per approved drawings.

The coarse aggregates shall not normally be spread more than 3 days in advance of thesubsequent construction operations.

404.3.5 Rolling : Immediately following the spreading of the coarse aggregates,rolling shall be started with three wheeled power rollers of 80 to 100 kN capacity or tandemor vibratory rollers of 80 to 100 kN static weight. The type of roller to be used shall beapproved by the Engineer based on trial run.

Except on superelevated portions where the rolling shall proceed from inner edge to theouter, rolling shall begin from the edges gradually progressing towards the center. Firstthe edge/edges shall be compacted with roller running forward and backward. The rollershall then move inward parallel to the center line of the road, in successive passes uniformlyoverlapping preceding tracks by at least one-half width.

Rolling shall be continued until the road metal is thoroughly keyed and the creaping ofstone ahead of the roller is no longer visible. During rolling, slight sprinkling of water maybe done, if necessary. Rolling shall not be done when the sub-grade is soft or yielding orwhen it causes a wave-like motion in the sub-grade or sub-base course.

The rolled surface shall be checked transversely with templates and longitudinally with3 m straight edge. Any irregularities, exceeding 12 mm, shall be corrected by looseningthe surface, adding or removing necessary amount of aggregates and re-rolling until theentire surface conforms to the desired camber and grade. In no case shall the use ofscreenings be permitted to make up depressions.

Material, which gets crushed excessively during compaction or becomes segregated, shallbe removed and replaced with suitable aggregates.

404.3.6 Application of screenings : After the coarse aggregates have been rolledto Clause 404.3.5, screenings to completely fill the interstices shall be applied graduallyover the surface. These shall not be damp or wet at the time of application. Dry rollingshall be done while the screenings are being spread so that vibrations of the roller cause

129


them to settle into the voids of the coarse aggregates. The screenings shall not be dumpedin piles but be spread uniformly in successive thin layers either by the spreading motionsof hand shovels or by mechanical spreaders, or directly from tipper with suitable gritspreading arrangement. Tipper operating for spreading the screenings shall be equippedwith pneumatic tyres and operated so as not to disturb the coarse aggregates.

The screenings shall be applied at a slow and uniform rate (in three or more applications)so as to ensure filling of all voids. This shall be accompanied by dry rolling and broomingwith mechanical brooms, hand brooms or both. In no case shall the screenings be appliedso fast and thick as to form cakes or ridges on the surface in such a manner as wouldprevent filling of voids or prevent the direct bearing of the roller on the coarse aggregates.The spreading, rolling, and brooming of screenings shall be carried out in only such lengthsof the road which could be completed within one day’s operation.

404.3.7 Sprinkling of water and grouting : After application of screenings, thesurface shall be copiously sprinkled with water, swept and rolled. Hand brooms shall beused to sweep the wet screenings into voids and to distribute them evenly. The sprinkling,sweeping and rolling operation shall be continued, with additional screenings applied asnecessary until the coarse aggregates have been thoroughly keyed, well-bonded and firmlyset in its full depth and a grout has been formed of screenings. Care shall be taken to seethat the sub-base or sub-grade does not get damaged due to the addition of excessivequantities of water during construction.

In case of lime treated soil sub-base, construction of water bound macadam on top of itcan cause excessive water to flow down to the lime treated sub-base before it has pickedup enough strength (is still “green”) and thus cause damage to the sub-base layer. Thelaying of water bound macadam layer in such cases shall be done after the sub-baseattains adequate strength, as directed by the Engineer.

404.3.8 Application of binding material : After the application of screenings inaccordance with Clauses 404.3.6 and 404.3.7, the binding material where it is requiredto be used (Clause 404.2.7) shall be applied successively in two or more thin layers at aslow and uniform rate. After each application, the surface shall be copiously sprinkled withwater, the resulting slurry swept in with hand brooms, or mechanical brooms to fill the voidsproperly, and rolled during which water shall be applied to the wheels of the rollers ifnecessary to wash down the binding material sticking to them. These operations shallcontinue until the resulting slurry after filling of voids, forms a wave ahead of the wheels ofthe moving roller. In case the aggregates are of a soft variety it would be preferred toreplace binder material with an equivalent amount of additional screenings.

404.3.9 Setting and drying : After the final compaction of water bound macadamcourse, the pavement shall be allowed to dry overnight. Next morning hungry spots shallbe filled with screenings or binding material as directed, lightly sprinkled with water if

130


necessary and rolled. No traffic shall be allowed on the road until the macadam has set.The Engineer shall have the discretion to stop hauling traffic from using the completedwater bound macadam course, if in his opinion it would cause excessive damage to thesurface.

The compacted water bound macadam course shall be allowed to completely dry and setbefore the next pavement course is laid over it.


404.4.1 The surface finish of construction shall conform to the requirements of Clause902.

404.4.2 Control on the quality of materials and works shall be exercised by theEngineer in accordance with Section 900.

404.4.3 The water bound macadam work shall not be carried out when theatmospheric temperature is less than 10°C in the shade.

404.4.4 Reconstruction of defective macadam : The finished surface of waterbound macadam shall conform to the tolerances of surface regularity as prescribed inClause 902. However, where the surface irregularity of the course exceeds the tolerancesor where the course is otherwise defective due to sub-grade soil mixing with theaggregates, the course to its full thickness shall be scarified over the affected area,reshaped with added material or removed and replaced with fresh material as applicableand re-compacted. The area treated shall not be less than 10 sq.m. In no case shalldepressions be filled up with screenings or binding material.

404.5 Arrangements for Traffic.

During the period of construction, the arrangements for traffic shall be done as perClause 112.


Water bound macadam shall be measured as finished work in position in cubic metres.

404.7 Rate

The Contract unit rate for water bound macadam sub-base/base course shall be payablein full for carrying out the required operations including full compensation for all componentslisted in Clause 401.8 (i) to (v), including arrangement of water used in the work as approvedby the Engineer.

131


405 CRUSHED CEMENT CONCRETE SUB-BASE/BASE

405.1 Scope

This work shall consist of breaking and crushing the damaged cement concrete slabs andre-compacting the same as sub-base/base course in one or more layers. Where specified,it shall also include treating the surface of the top layer with a penetration coat of bitumen.The work shall be performed on such widths and lengths as may be specified, in accordancewith the requirements of these Specifications and in conformity with the lines, grades andcross-sections shown on the drawings or as otherwise directed by the Engineer.

405.2 Materials

405.2.1 Coarse aggregates : Coarse aggregates for this work shall be brokencement concrete slabs crushed to a size not exceeding 75 mm and as far as possible,conforming to one of the gradings given in Table 400-7.

405.2.2 Key aggregates : Key aggregate for the penetration coat shall consist ofcrushed stone, crushed gravel, shingle or other stones. It shall be clean, strong, durable, offairly cubical shape and free of disintegrated pieces, organic or other deleterious matterand adherent coating. The aggregates shall be hydrophobic and of low porosity.

The aggregate shall be 11.2 mm size defined as 100 percent passing through 13.2 mmsieve and retained on 5.6 mm sieve and shall satisfy the physical requirements set forth inTable 500-3.

405.2.3 Binder : Binder for the penetration coat for the top layer shall be bitumen ofa suitable grade, as directed by the Engineer and satisfying the requirements of IS:73,217 or 454, as applicable or any approved cutback or emulsion, satisfying the requirementsof IS:8887.


405.3.1 General : Crushed cement concrete sub-base/base course may beconstructed in one or two layers, depending upon the thickness of the concrete slabsdismantled and crushed. The thickness of each layer shall, however, not exceed 100 mmin case of sub-base and 75 mm in case of base course.

The course shall be constructed as water bound macadam to Clause 404, using crushedcement concrete as coarse aggregates except that no screenings or binding materialneed be applied. Where specified, the top layer shall be treated with a penetration coat ofbinder described in Clause 405.3.2.

132


405.3.2 Application of penetration coat over the top layer : Before theapplication of the penetration coat, the surface shall be cleaned of dust, dirt and otherforeign matter, using mechanical broom or any other equipment specified by the Engineer.Dust removed in the process shall be blown off with the help of compressed air.

The binder shall be heated to the temperature appropriate to the grade of bitumen usedand sprayed on the dry surface in a uniform manner at the rate of 25 kg per 10 m2 area interms of the residual bitumen with the help of either self-propelled or towed bitumen pressuresprayer with self-heating arrangement and spray nozzle capable of spraying bitumen atspecified rates and temperatures so as to provide a uniform unbroken spread of bitumen.Excessive deposits of binder caused by stopping or starting of the sprayer or throughleakage or any other cause shall be suitably corrected.

Immediately after the application of binder, the key aggregates, in a clean and dry stateshall be spread uniformly on the surface at the rate of 0.13 m3 per 10 m2 area, preferably bymeans of a mechanical gritter, capable of spreading aggregates uniformly at specifiedrates or otherwise manually with the approval of the Engineer, so as to cover the surfacecompletely. Immediately after the application of the key aggregates, the entire surfaceshall be rolled to Clause 506.3.8.


The surface finish and control on the quality of materials and works shall be exercised bythe Engineer in accrodance with section 900.


During the period of construction, arrangement for traffic shall be done as per Clause 112.


Breaking the existing cement concrete pavement slabs, crushing and recompacting theslab material as sub-base/base course shall be measured as a single item in terms of thevolume of sub-base/base laid in position in cubic metres.

Penetration coat shall be measured as finished work in square metres.

405.7 Rate

405.7.1 The Contract unit rate for crushed cement concrete sub-base/base course shallbe payment in full for carrying out the required operations including full compensation for:

i) making arrangements for traffic to Clause 112 except for initialtreatment to verges/shoulders and construction of diversions;

133


ii) breaking the cement concrete slabs, crushing, sieving andrecompacting the slab material as sub-base/base course;

iii) all labour, tools, equipment and incidentals to complete the work tothe Specifications; and

iv) carrying out the work in part widths of road where directed.

405.7.2 The Contract unit rate for penetration coat shall be payment in full for carryingout the required operations including full compensation for all components listed in Clause504.8.

406 WET MIX MACADAM SUB-BASE/BASE

406.1 Scope

This work shall consist of laying and compacting clean, crushed, graded aggregate andgranular material, premixed with water, to a dense mass on a prepared sub-grade/sub-base/base or existing pavement as the case may be in accordance with the requirementsof these Specifications. The material shall be laid in one or more layers as necessary tolines, grades and cross-sections shown on the approved drawings or as directed by theEngineer.

The thickness of a single compacted Wet Mix Macadam layer shall not be less than 75mm. When vibrating or other approved types of compacting equipment are used, thecompacted depth of a single layer of the sub-base course may be upto 200 mm with theapproval of the Engineer.

406.2 Materials

406.2.1 Aggregates

406.2.1.1 Physical requirements : Coarse aggregates shall be crushed stone. Ifcrushed gravel/shingle is used, not less than 90 percent by weight of the gravel/shinglepieces retained on 4.75 mm sieve shall have at least two fractured faces. The aggregatesshall conform to the physical requirements set forth in Table 400-9.

If the water absorption value of the coarse aggregate is greater than 2 percent, thesoundness test shall be carried out on the material delivered to site as per IS:2386(Part-5).

406.2.1.2 Grading requirements : The aggregates shall conform to the grading givenin Table 400-10.

134


Table 400-9 Physical Requirements of Coarse Aggregates for Wet Mix Macadamfor Sub-base/Base Courses

S. Test Test Method RequirementsNo.1. Los Angeles IS:2386 (Part-4) 40 percent (Max.)

Abrasion value

Aggregate IS:2386 (Part-4) 30 percent (Max.)Impact value or IS:5640

2. Combined Flakiness and IS:2386 (Part-1) 40 percent (Max.)*Elongation indices (Total)

* To determine this combined proportion, the flaky stone from a representative sampleshould first be separated out. Flakiness index is weight of flaky stone metal dividedby weight of stone sample. Only the elongated particles be separated out from theremaining (non-flaky) stone metal. Elongation index is weight of elongated particlesdivided by total non-flaky particles. The values of flakiness index and elongationindex so found are added up.

Table 400-10 Grading Requirements of Aggregates for Wet Mix Macadam

IS Sieve Per cent by weight passing the IS SieveDesignation Grade 1 layer thickness ≥≥≥≥≥ 100mm Grade 2<100 mm

53.00 mm 10045.00 mm 95 – 10026.50 mm _ 10022.40 mm 60 – 80 50-10011.20 mm 40 – 60 -4.75 mm 25 – 40 35-552.36 mm 15 – 30 -

600.00 micron 8 – 22 10-3075.00 micron 0 – -5 2-5

Material finer than 425 micron shall have Plasticity Index (PI) not exceeding 6.

The final gradation approved within these limits shall be graded from coarse to fine andshall not vary from the low limit on one sieve to the high limit on the adjacent sieve or viceversa.

135



406.3.1 Preparation of base : Clause 404.3.1 shall apply.

406.3.2 Provision of lateral confinement of aggregates : While constructing wetmix macadam, arrangement shall be made for the lateral confinement of wet mix. Thisshall be done by laying materials in adjoining shoulders along with that of wet mix macadamlayer and following the sequence of operations described in Clause 407.4.1.

406.3.3 Preparation of mix : Wet Mix Macadam shall be prepared in an approvedmixing plant of suitable capacity having provision for controlled addition of water and forced/positive mixing arrangement like pugmill or pan type mixer of concrete batching plant. Theplant shall have following features:

i) Cold aggregates with minimum four bin feeders with variable speedmotor

ii) Vibrating screen for removal of oversize aggregates

iii) Conveyor Belt

iv) Controlled system for addition of water

v) Forced/positive mixing arrangement like pug-mill or pan type

vi) Anti-segregation hydraulically operated gob/surge hopper

vii) Centralized control panel for sequential operation of various devicesand precise process control

viii) Safety devices

Optimum moisture for mixing shall be determined in accordance with IS:2720 (Part-8)after replacing the aggregate fraction retained on 22.4 mm sieve with material of 4.75 mmto 22.4 mm size. While adding water, due allowance should be made for evaporationlosses. However, at the time of compaction, water in the wet mix should not vary from theoptimum value by more than agreed limits. The mixed material should be uniformly wetand no segregation should be permitted.

406.3.4 Spreading of mix : Immediately after mixing, the aggregates shall be spreaduniformly and evenly upon the prepared sub-grade/sub-base/base in required quantities.In no case shall these be dumped in heaps directly on the area where these are to be laidnor shall their hauling over a partly completed stretch be permitted.

136


The mix may be spread by a paver finisher. The paver finisher shall be self-propelled, ofrepute make, proven design and adequate capacity with following features:-

i) Tractor unit shall have crawler tracks or pneumatic tyre.

ii) Racks provide greater traction and suitable to work on soft or loosesub-bases and laying large width up to 10 m or more. Wheeled paveris faster and normally preferred to work on hard surfaces with widthup to 8 m.

iii) Material distribution system comprising of hopper, two conveyor beltseach working independently, conveyor speed adjustable with limitswitches and auger system easily capable of raising and lower; toprovide a smooth uninterrupted material flow for different layerthicknesses from the tipper to the screed.

iv) Hydraulically operated telescopic screed for paving width upto to8.5 m and fixed screed beyond this. The screed shall have tampingand vibrating arrangement for initial compaction of the layer.

v) The drive shall be hydrostatic with infinite variable speed.

vi) Automatic leveling control system with electronic sensing device tomaintain mat thickness and cross slope of mat during layingprocedure.

In exceptional cases where it is not possible for the paver to be utilized, mechanical meanslike motor grader may be used with the prior approval of the Engineer. The motor gradershall be capable of spreading the material uniformly all over the surface. For portions wheremechanical means cannot be used, manual means as approved by the Engineer shall beused only in restricted areas.

The surface of the aggregate shall be carefully checked with templates and all high or lowspots remedied by removing or adding aggregate as may be required. The layer may betested by depth blocks during construction. No segregation of larger and fine particlesshould be allowed. The aggregates as spread should be of uniform gradation with nopockets of fine materials.

The Engineer may permit manual mixing and /or laying of wet mix macadam where smallquantity of wet mix macadam is to be executed. Manual mixing/laying in inaccessible/remote locations and in situations where use of machinery is not feasible can also bepermitted. Where manual mixing/laying is intended to be permitted, the same shall beindicated in the Contract.

406.3.5 Compaction : After the mix has been laid to the required thickness, gradeand crossfall/camber the same shall be uniformly compacted to the full depth with suitable

137


roller. If the thickness of single compacted layer does not exceed 200 mm, a smoothwheel roller of 80 to 100kN weight may be used. For a compacted single layer upto 200mm, the compaction shall be done with the help of vibratory roller of minimum static weightof 80 to 100 kN with on amplitude not exceeding 0.7 mm or equivalent capacity roller. Thespeed of the roller shall not exceed 5 km/h.

In portions having unidirectional cross fall/superelevation, rolling shall commence from thelower edge and progress gradually towards the upper edge. Thereafter, roller shouldprogress parallel to the center line of the road, uniformly over-lapping each precedingtrack by at least one-third width until the entire surface has been rolled. Alternate trips ofthe roller shall be terminated in stops at least 1 m away from any preceding stop.

In portions in camber, rolling should begin at the edge with the roller running forward andbackward until the edges have been firmly compacted. The roller shall then progressgradually towards the center parallel to the center line of the road uniformly overlappingeach of the preceding track by at least one-third width until the entire surface has beenrolled.

Any displacement occurring as a result of reversing of the direction of a roller or from anyother cause shall be corrected at once as specified and/or removed and made good.

Along forms, kerbs, walls or other places not accessible to the roller, the mixture shall bethoroughly compacted with mechanical tampers or a plate compactor. Skin patching of anarea without scarifying the surface to permit proper bonding of the added material shallnot be permitted.

Rolling should not be done when the sub-grade is soft or yielding or when it causes awave-like motion in the sub-base/base course or sub-grade. If irregularities develop duringrolling which exceed 12 mm when tested with a 3 m straight edge, the surface should beloosened and premixed material added or removed as required before rolling again so asto achieve a uniform surface conforming to the desired grade and crossfall. In no caseshall the use of unmixed material be permitted to make up the depressions.

Rolling shall be continued till the density achieved is at least 98 percent of the maximumdry density for the material as determined by the method outlined in IS:2720 (Part-8).

After completion, the surface of any finished layer shall be well-closed, free from movementunder compaction equipment or any compaction planes, ridges, cracks and loose material.All loose, segregated or otherwise defective areas shall be made good to the full thicknessof the layer and recompacted.

406.3.6 Setting and drying : After final compaction of wet mix macadam course,the road shall be allowed to dry for 24 hours.

138


406.4 Opening to Traffic

No vehicular traffic of any kind should be allowed on the finished wet mix macadam surface.


406.5.1 Surface evenness : The surface finish of construction shall conform to therequirements of Clause 902.

406.5.2 Quality control : Control on the quality of materials and works shall beexercised by the Engineer in accordance with Section 900.

406.6 Rectification of Surface Irregularity

Where the surface irregularity of the wet mix macadam course exceeds the permissibletolerances or where the course is otherwise defective due to sub-grade soil getting mixedwith the aggregates, the full thickness of the layer shall be scarified over the affected area,re-shaped with added premixed material or removed and replaced with fresh premixedmaterial as applicable and recompacted in accordance with Clause 406.3. The areatreated in the aforesaid manner shall not be less than 5 m long and 2 m wide. In no caseshall depressions be filled up with unmixed and ungraded material or fines.

406.7 Arrangement for Traffic

During the period of construction, arrangements for traffic shall be done as perClause 112.


Wet mix macadam shall be measured as finished work in position in cubic metres.

406.9 Rate

The Contract unit rate for wet mix macadam shall be payment in full for carrying out therequired operations including full compensation for all components listed in Clause 401.8.

407 SHOULDERS, ISLANDS AND MEDIANS

407.1 Scope

The work shall consist of constructing shoulder (hard/paved/earthen with brick or stoneblock edging) on either side of the pavement, median in the road dividing the carriageway

139


into separate lanes and islands for channelising the traffic at junctions in accordance withthe requirements of these Specifications and in conformity with the lines, grades and cross-sections shown on the drawings or as directed by the Engineer.

407.2 Materials

Shoulder on either side of the road may be of selected earth/granular material/pavedconforming to the requirements of Clause 305/401 and the median may be of selectedearth conforming to the requirements of Clause 305.

Median/Traffic islands shall be raised and kerbed at the perimeter and the enclosed areafilled with earth and suitably covered with grass turf/shrubs as per Clause 307 and/or pavedas per Clause 409.3.4 or 409.3.5.

Paved shoulders shall consist of sub-base, base and surfacing courses, as shown in thedrawings and materials for the same shall conform to relevant Specifications of thecorresponding items. Where paved or hard shoulders are not provided, the pavementshall be provided with brick/stone block edgings as shown in the drawings. The brick shallconform to Clause 1003 of these Specifications. Stone blocks shall conform to Clause1004 of these Specifications and shall be of size 225 mm x 110 mm x 75 mm.

407.3 Size of Shoulders/Medians/Islands

Shoulder (earthen/hard/paved)/median/traffic island dimensions shall be as shown on thedrawings or as directed by the Engineer.


407.4.1 Shoulders : The sequence of operations shall be such that the constructionof paved shoulder is done in layers each matching the thickness of adjoining pavementlayer. Only after a layer of pavement and corresponding layers in paved and earth shoulderportion have been laid and compacted, the construction of next layer of pavement andshoulder shall be taken up.

Where the materials in adjacent layers are different, these shall be laid together and thepavement layer shall be compacted first. The corresponding layer in paved shoulder portionshall be compacted thereafter, which shall be followed by compaction of each shoulderlayer. The adjacent layers having same material shall be laid and compacted together.

In all cases where paved shoulders have to be provided along side of existing carriageway,the existing shoulders shall be excavated in full width and to the required depth as perClause 301.3.7. Under no circumstances, box cutting shall be done for construction ofshoulders.

140


Compaction requirement of earthen shoulder shall be as per Table 300-2. In the case ofbituminous courses, work on shoulder (earthen/hard/paved), shall start only after thepavement course has been laid and compacted.

During all stages of shoulder (earthen/hard/paved) construction, the required crossfall shallbe maintained to drain off surface water.

Regardless of the method of laying, all shoulder construction material shall be placed directlyon the shoulder. Any spilled material dragged on to the pavement surface shall beimmediately removed, without damage to the pavement, and the area so affected thoroughlycleaned.

407.4.2 Median and Islands : Median and islands shall be constructed in a mannersimilar to shoulder up to the road level. Thereafter, the median and islands, if raised, shallbe raised at least 300 mm by using kerb stones of approved material and dimensions andsuitably finished and painted as directed by the Engineer. If not raised, the median andislands shall be differentiated from the shoulder/pavement as the case may be, as directedby the Engineer. The confined area of the median and islands shall be filled with localearth or granular material or any other approved material and compacted by platecompactor/power rammer. The confined area after filling with earth shall be turfed withgrass or planted with shrubs and in case of granular fill it can be finished with tiles/slabs asdirected by the Engineer.

407.4.3 Brick/stone block edging : The brick/stone blocks shall be laid on edge,with the length parallel to the transverse direction of the road. They shall be laid on a bedof 25 mm sand, set carefully rolled into position by a light roller and made flush with thefinished level of the pavement.

407.5 Surface Finish and Quality Control of Works

The surface finish of construction shall conform to the requirements of Clause 902. Controlon the quality of materials and works shall be exercised by the Engineer in accordancewith Section 900.


Shoulder (earthen/hard/paved), island and median construction shall be measured asfinished work in position as below:

i) For excavation in cu.m.ii) For earthwork/granular fill in cu.m.

141


iii) For sub-base, base, surfacing courses in units as for respective itemsiv) For kerb in running metersv) For turfing and tile/slab finish in sq.m.vi) For brick/stone block edging in sq.m.

407.7 Rate

The Contract unit rate for shoulder (hard/paved/earthen with brick or stone block edging),island and median construction shall be payment in full for carrying out the requiredoperations including full compensation for all components listed in Clause 401.8 (i) to (v)as applicable. The rate for brick/stone block edging shall include the cost of sand cushion.

408. CEMENT CONCRETE KERB AND KERB WITH CHANNEL

408.1 Scope

This work shall consist of constructing cement concrete kerbs and kerbs with channel inthe central median and/or along the footpaths or separators in conformity with the lines,levels and dimensions as specified in the drawings or as directed by the Engineer.

408.2 Materials

Kerbs and kerb with channel shall be provided in cement concrete of Grade M 20 inaccordance with Section 1700 of these Specifications.

408.3 Type of Construction

These shall be cast-in-situ construction with suitable kerb casting machine in all situationsexcept at locations where continuous casting with equipment is not practicable. In thoselocations precast concrete blocks shall be used.

408.4 Equipment

A continuous kerb casting equipment of adequate capacity and controls, capable of layingthe kerbs in required cross-sections and producing a well-compacted mass of concretefree of voids and honeycombs, shall be used.


408.5.1 Kerb shall be laid on firm foundation of minimum 150 mm thickness of cementconcrete of M 15 grade cast in-situ or on extended width of pavement. The foundationshall have a projection of 50 mm beyond the kerb stone. Before laying the foundation oflean concrete, the base shall be leveled and slightly watered to make it damp.

142


408.5.2 In the median portions in the straight reaches, the kerb shall be cast incontinuous lengths. In the portions where footpath is provided and/or the slope of thecarriageway is towards median (as in case of superelevated portion), there shall be sufficientgap/recess left in the kerb to facilitate drainage openings.

408.5.3 After laying the kerbs and just prior to hardening of the concrete, saw cutgrooves shall be provided at 5 m intervals up to FRL or as specified by the Engineer.

408.5.4 Kerbs on the drainage ends such as along the footpath or the median insuperelevated portions, shall be cast with monolithic concrete channels as indicated indrawings. The slope of the channel towards drainage pipes shall be ensured for efficientdrainage of the road surface.

408.5.5 Vertical and horizontal tolerances with respect to true line and level shall be+6 mm.


Cement concrete kerb/kerb with channel shall be measured in linear metre for the completeitem of work.

Foundation of kerb, where separately provided shall be measured in linear metre forcomplete item of work.

408.7 Rate

The Contract unit rates for cement concrete kerb/kerb with channel and foundation forkerb shall be payment in full compensation for furnishing all materials, labour, tools,equipment for construction and other incidental cost necessary to complete the work.

409 FOOTPATHS AND SEPARATORS

409.1 Scope

The work shall consist of constructing footpaths and/or separators at locations as specifiedin the drawings or as directed by the Engineer.

The lines, levels and dimensions shall be as per the drawings. The scope of the work shallinclude provision of all drainage arrangements as shown in the drawings or as directed bythe Engineer.

143


409.2 Materials

The footpaths and separators shall be constructed with any of the following types:

a) Cast-in-situ cement concrete of Grade M 20 as per Section 1700 ofthe Specifications.

b) Precast cement concrete blocks/tiles of Grade M 20 as per Section1700 of the Specifications. The minimum thickness of the cementconcrete block/tile shall be 25 mm and minimum size shall be 300mm x 300 mm.

c) Natural stone slab cut and dressed from stone of good and soundquality, uniform in texture, free from defects and at least equal to asample submitted by the Contractor and approved by the Engineer.The minimum thickness of the natural stone slab shall be 25 mm andminimum size shall be 300 mm x 300 mm.


409.3.1 Drainage pipes below the footpath originating from the kerbs shall be firstlaid in the required slope and connected to the drains/sumps/storm water drain/drainagechutes as per provisions of the drawings, or as specified.

409.3.2 Portion on back side of kerbs shall be filled and compacted with granularsub-base material as per Clause 401 of the Specifications in specified thickness.

409.3.3 The base shall be prepared and finished to the required lines, levels anddimensions as indicated in the drawing with the following:

a) Minimum 150 mm thick, compacted granular sub-base material asper Clause 401 of the Specifications.

b) Minimum 25 mm thick cement concrete of Grade M 15.

Over the prepared base, precast concrete blocks/tiles/natural stone slabs and/or cast-in-situ slab shall be set/laid as described in Clauses 409.3.4 and 409.3.5.

409.3.4 Precast cement concrete blocks/tiles/natural stone slabs : The blocks/tiles/slabs shall be set on a layer of average 12 mm thick cement-sand mortar (1:3) laid onprepared base in such a way that there is no rocking. The gaps between the blocks/tiles/slabs shall not be more than 12 mm and shall be filled with cement-sand mortar (1:3).

409.3.5 Cast-in-situ cement concrete : The minimum thickness of the cementconcrete shall be 25 mm and it shall be cast on the prepared base in panels of specifiedsize in a staggered manner. Construction joints shall be provided as per Section 1700 ofthe Specifications.

144



Footpaths and separators shall be measured in sq.m between inside of kerbs.

409.5 Rate

Contract unit rates shall be inclusive of full compensation of all labour, materials, tools,equipment and incidentals to construction of footpaths. Cost of providing pipes andarrangement for their discharge into appropriate drainage channels shall be incidental tothe construction of footpaths.

410 CRUSHER-RUN MACADAM BASE

410.1 Scope

This work shall consist of furnishing, placing and compacting crushed stone aggregatesub-base and base courses constructed in accordance with the requirements set forth inthese Specifications and in conformity with the lines, grades, thickness and cross-sectionsshown on the plans or as directed by the Engineer.

410.2 Materials

The material to be used for the work shall be crushed rock. If crushed gravel/shingle isused, not less than 90 percent by weight of the gravel/shingle pieces retained on 4.75 mmsieve shall have at least two fractured faces. It shall be free from any organic matter andother deleterious substances and shall be of such nature that it can be compacted readilyunder watering and rolling to form a firm, stable base. The aggregates shall conform to thegrading and quality requirements given in Tables 400-11 and 400-12.

At the option of the Contractor, the grading for either 53 mm maximum size or 37.5 mmmaximum size shall be used, except that once a grading is selected, it shall not be changedwithout the Engineer’s approval.

410.3. Construction Operations

410.3.1 Preparation of subgrade : Any ruts, deformations or soft yielding placeswhich occur in the sub-base or sub-grade shall be corrected and compacted to the requireddensity before the aggregate base course is placed thereon.

410.3.2 Spreading, watering, mixing and compaction : The aggregate shall beuniformly deposited on the approved subgrade by means of hauling vehicle with or withoutspreading devices. Aggregate will be distributed over the surface to the depth specifiedon the plans or as directed by the Engineer.

145


Table 400.11 Aggregate Grading Requirements

Sieve Size Per cent passing by weight

53 mm max. size 37.5 mm max. size

63 mm 10045 mm 87 – 100 10022.4 mm 50 – 85 90 – 1005.6 mm 25 – 45 35 – 55710 mm 10 – 25 10 – 30 90 mm 2 – 5 2 – 5

Table 400.12 Physical Requirements of Coarse Aggregates forCrusher-run Macadam Base

Test Test Method Requirements

1. Los Angeles IS:2386 40 maximumAbrasion value (Part-4)

Aggregate IS:2386 30 maximumImpact value (Part-4) or

IS:5640

2. Combined Flakiness and IS:2386 40 maximum**Elongation Indices (Total) (Part-1)

3 *Water absorption IS:2386 2 percent maximum(Part-3)

4. Liquid Limit of IS:2720 25 maximummaterial passing 425 micron (Part-5)

5. Plasticity Index of material IS:2720 6 maximumpassing 425 micron (Part-5)

* If the water absorption is more than 2 percent, soundness test shall be carried outas per IS:2386 (Part-5)

** To determine this combined proportion, the flaky stone from a representative sampleshould first be separated out. Flakiness index is weight of flaky stone metal dividedby weight of stone sample. Only the elongated particles be separated out from theremaining (non-flaky) stone metal. Elongation index is weight of elongated particlesdivided by total non-flaky particles. The value of flakiness index and elongationindex so found are added up.

146


After the base course material has been deposited, it shall be thoroughly blade-mixed tofull depth of the layer by alternately blading the entire layer to the center and back to theedges of the road. It shall then be spread and finished to the required cross-section bymeans of a motor grader.

Water shall be applied prior to and during all blading and processing operations to moistenthe material sufficiently to prevent segregation of the fine and coarse particles. Watershall be applied in sufficient amounts during construction to assist in compaction.

Compaction shall commence immediately after the spreading operation. If the thicknessof single compacted layer does not exceed 100 mm, a smooth wheel roller of 80 to 100 kNweight may be used. For a compacted single layer upto 200 mm, compaction shall bedone with the help of vibratory roller of minimum static weight of 80 to 100 kN or equivalentcapacity. The speed of the roller shall not exceed 5 km/h. Each layer of material shall becompacted to not less than 98 percent of the maximum density as determined byIS:2720 (Part-8).



Control on the quality of materials and work shall be exercised by the Engineer inaccordance with Section 900.


During the period of construction, arrangements for traffic shall be done in accordancewith Clause 112.


Crusher-run macadam base shall be measured as finished work in position in cubic metres.

410.7 Rate

The Contract unit rate for crusher run macadam base shall be payment in full for carryingout the required operations including full compensation for all components as inClause 401.8 (i) to (v).

section_40078021adasad27814

Documents